U.S. patent number 8,599,088 [Application Number 11/959,191] was granted by the patent office on 2013-12-03 for dual-band antenna with angled slot for portable electronic devices.
This patent grant is currently assigned to Apple Inc.. The grantee listed for this patent is Enrique Ayala, Bing Chiang, Douglas B. Kough, Matthew Ian McDonald, Gregory Allen Springer, Hao Xu. Invention is credited to Enrique Ayala, Bing Chiang, Douglas B. Kough, Matthew Ian McDonald, Gregory Allen Springer, Hao Xu.
United States Patent |
8,599,088 |
Chiang , et al. |
December 3, 2013 |
Dual-band antenna with angled slot for portable electronic
devices
Abstract
Dual slot antennas are provided for portable electronic devices
such as handheld electronic devices. A dual slot antenna may have
an open slot that has an open end that is not encircled by
conductive material and may have a closed slot in which each end is
surrounded by conductor. The closed and open slots may have
portions that run parallel to each other. The antenna may be fed
using feed terminals that bridge the closed and open slots in the
vicinity of the portions of the slots that run parallel to each
other. The slots may have portions that are angled with respect to
each other. An end portion of one of the slots may be bent and
widened for impedance matching and broadened bandwidth. Other
portions of the slots may also be angled with respect to their main
longitudinal axes.
Inventors: |
Chiang; Bing (Cupertino,
CA), Springer; Gregory Allen (Sunnyvale, CA), Kough;
Douglas B. (San Jose, CA), Ayala; Enrique (Watsonville,
CA), McDonald; Matthew Ian (San Jose, CA), Xu; Hao
(Cupertino, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Chiang; Bing
Springer; Gregory Allen
Kough; Douglas B.
Ayala; Enrique
McDonald; Matthew Ian
Xu; Hao |
Cupertino
Sunnyvale
San Jose
Watsonville
San Jose
Cupertino |
CA
CA
CA
CA
CA
CA |
US
US
US
US
US
US |
|
|
Assignee: |
Apple Inc. (Cupertino,
CA)
|
Family
ID: |
39873988 |
Appl.
No.: |
11/959,191 |
Filed: |
December 18, 2007 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20090153411 A1 |
Jun 18, 2009 |
|
Current U.S.
Class: |
343/770 |
Current CPC
Class: |
H01Q
13/10 (20130101); H01Q 1/243 (20130101); H01Q
5/371 (20150115) |
Current International
Class: |
H01Q
13/10 (20060101) |
Field of
Search: |
;343/767,770 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1700514 |
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Nov 2005 |
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CN |
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1930731 |
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Mar 2007 |
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CN |
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2935501 |
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Aug 2007 |
|
CN |
|
200969391 |
|
Oct 2007 |
|
CN |
|
198 17 573 |
|
Oct 1999 |
|
DE |
|
2004 266573 |
|
Sep 2004 |
|
JP |
|
Other References
Jacob, N. et al. "Investigationof Wide-Band Microstrip Slot
Antenna." IEEE Transactions on Antennas and Propagation. vol. 52,
No. 3, p. 865-872, Mar. 2004. cited by applicant .
Hill et al. U.S. Appl. No. 11/650,187, filed Jan. 4, 2007. cited by
applicant .
Hill et al. U.S. Appl. No. 11/821,192, filed Jun. 21, 2007. cited
by applicant .
Hill et al. U.S. Appl. No. 11/897,033, filed Aug. 28, 2007. cited
by applicant .
Zhang et al. U.S. Appl. No. 11/895,053, filed Aug. 22, 2007. cited
by applicant .
Chiang et al. U.S. Appl. No. 11/702,039, filed 2/1/07. cited by
applicant .
R. Bancroft "A Commercial Perspective on the Development and
Integration of an 802.11a/b/g HiperLan/WLAN Antenna into Laptop
Computers", IEEE Antennas and Propagation Magazine, vol. 48, No. 4,
Aug. 2006, pp. 12-18. cited by applicant .
B. Chiang et al. "Invasion of Inductor and Capacitor Chips in the
Design of Antennas and Platform Integration", IEEE International
Conference on Portable Information Devices, May 2007, pp. 1-4.
cited by applicant .
A. Lai et al. "Infinite Wavelength Resonant Antennas With Monopolar
Radiation Pattern Based on Periodic Structures", IEEE Transactions
on Antennas and Propagation, vol. 55, No. 3, Mar. 2007, pp.
868-876. cited by applicant.
|
Primary Examiner: Karacsony; Robert
Attorney, Agent or Firm: Treyz Law Group Treyz; G. Victor
Lyons; Michael H.
Claims
What is claimed is:
1. A handheld electronic device comprising: transceiver circuitry;
a transmission line coupled to the transceiver circuitry; and an
antenna that is coupled to the transmission line, wherein the
antenna has a ground plane that has dielectric-filled openings
defining a first slot and a second slot, wherein the first slot has
a main longitudinal axis, wherein the second slot has a main
longitudinal axis, wherein the first and second slots are oriented
so that the main longitudinal axis of the first slot is oriented at
an angle of between 5.degree. and 85.degree. with respect to the
main longitudinal axis of the second slot, wherein the ground plane
is configured so that the second slot has a straight portion with a
longitudinal axis that is oriented parallel to the main
longitudinal axis of the first slot, wherein the second slot has a
first width in the straight portion, wherein the ground plane is
further configured to define an end portion of the second slot that
has a longitudinal axis that is angled with respect to the
longitudinal axis of the straight portion of the second slot and
that has a second width that is larger than the first width in the
straight portion, wherein the second width is perpendicular to the
longitudinal axis of the end portion of the second slot, and
wherein the end portion is substantially rectangular in shape and
has a longitudinal axis that is oriented perpendicular to the
longitudinal axis of the straight portion.
2. The handheld electronic device defined in claim 1 wherein the
antenna has first and second antenna feed terminals, the handheld
electronic device further comprising: a dielectric support
structure having first and second conductive vias that are coupled
to first and second antenna feed terminals.
3. A dual slot handheld electronic device antenna formed from a
ground plane, comprising: an open slot in the ground plane that has
an open end; and a closed slot in the ground plane that has a first
portion that is oriented along a main longitudinal axis of the
closed slot and that has a first width and that has first and
second ends that are enclosed by conductive portions, wherein the
second end of the closed slot has a longitudinal axis that is
angled with respect to the main longitudinal axis of the closed
slot and has a second width that is perpendicular to the
longitudinal axis of the second end of the closed slot, wherein the
second width is larger than the first width, wherein the first end
of the closed slot has a longitudinal axis that is angled with
respect to the main longitudinal axis of the closed slot and has a
third width that is perpendicular to the longitudinal axis of the
first end of the closed slot, and wherein the third width is
approximately equal to the first width.
4. The dual slot handheld electronic device antenna defined in
claim 3 wherein the open slot has a length of at least 10 mm and
operates at 2.4 GHz and wherein the closed slot has a length of at
least 10 mm and operates at 5.4 GHz.
5. The dual slot handheld electronic device antenna defined in
claim 4 wherein the open slot has no angled portions and wherein
the closed slot has at least one portion that is angled away from
the open slot.
Description
BACKGROUND
This invention relates to antennas, and more particularly, to
antennas for portable electronic devices.
Due in part to their mobile nature, portable electronic devices are
often provided with wireless communications capabilities. Portable
electronic devices may use wireless communications to communicate
with wireless base stations. For example, cellular telephones may
communicate using cellular telephone bands at 850 MHz, 900 MHz,
1800 MHz, and 1900 MHz (e.g., the main Global System for Mobile
Communications or GSM cellular telephone bands). Portable
electronic devices may also use other types of communications
links. For example, portable electronic devices may communicate
using the Wi-Fi.RTM. (IEEE 802.11) bands at 2.4 GHz and 5.4 GHz and
the Bluetooth.RTM. band at 2.4 GHz. Communications are also
possible in data service bands such as the 3 G data communications
band at 2100 MHz band (commonly referred to as UMTS or Universal
Mobile Telecommunications System).
To satisfy consumer demand for small form factor wireless devices,
manufacturers are continually striving to reduce the size of
components that are used in these devices. For example,
manufacturers have made attempts to miniaturize the antennas used
in portable electronic devices.
A typical antenna may be fabricated by patterning a metal layer on
a circuit board substrate or may be formed from a sheet of thin
metal using a foil stamping process. These techniques can be used
to produce antennas that fit within the tight confines of a compact
portable device such as a handheld electronic device. With
conventional portable electronic devices, however, design
compromises are made to accommodate compact antennas. These design
compromises may include, for example, compromises related to
antenna efficiency and antenna bandwidth.
It would therefore be desirable to be able to provide improved
antennas for portable electronic devices.
SUMMARY
Multiband slot antennas are provided for portable electronic
devices such as handheld electronic devices. The multiband slot
antennas may have a ground plane element with first and second
openings that define respective first and second dielectric-filled
slots. The first slot may be an open slot that has an air-filled
end. The second slot may be a closed slot having ends that are
surrounded by portions of the ground plane.
The open and closed slots may each have a main longitudinal axes.
The main longitudinal axis of the closed slot may be angled with
respect to the main longitudinal axis of the open slot. The slots
may have additional angled portions and may have straight portions
that run parallel to each other. The antenna may be fed using
antenna terminals that bridge the first and second slots in the
vicinity of the straight portions.
An end portion of one of the slots may be angled and widened with
respect to the remainder of that slot for impedance matching and to
enhance the bandwidth associated with that slot.
The first and second slots may be formed in part of a conductive
portable electronic device housing. A dielectric support structure
with conductive vias may be used to route signals from antenna feed
terminals across the first and second slots.
Further features of the invention, its nature and various
advantages will be more apparent from the accompanying drawings and
the following detailed description of the preferred
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an illustrative portable electronic
device such as a handheld electronic device in accordance with an
embodiment of the present invention.
FIG. 2 is a schematic diagram of an illustrative portable
electronic device in accordance with an embodiment of the present
invention.
FIG. 3 is a diagram of an illustrative dual slot antenna in which
one of the slots has an angled portion in accordance with an
embodiment of the present invention.
FIG. 4 is a graph showing the performance of an illustrative dual
slot antenna in which an end portion of the slot that handles the
higher-frequency band is widened to enhance the bandwidth of the
higher-frequency band in accordance with an embodiment of the
present invention.
FIG. 5 is a diagram of an illustrative dual slot antenna with an
alternative open slot configuration in accordance with an
embodiment of the present invention.
FIG. 6 is a diagram of an illustrative dual slot antenna with an
angled slot and a substantially straight slot having a relatively
short angled portion in accordance with an embodiment of the
present invention.
FIG. 7 is a diagram of an illustrative dual slot antenna having an
angled slot with a relatively short angled portion at one of its
ends in accordance with an embodiment of the present invention.
FIG. 8 is a cross-sectional side view of an illustrative dual slot
antenna formed in a portable electronic device housing in
accordance with an embodiment of the present invention.
DETAILED DESCRIPTION
The present invention relates generally to electronic devices, and
more particularly, to antennas for wireless electronic devices.
The wireless electronic devices may be portable electronic devices
such as laptop computers, tablet computers, wireless access point
base stations such as IEEE 802.11 base stations, plug-in relay
stations such as those for IEEE 802.11 communications, or small
portable computers of the type that are sometimes referred to as
ultraportables. Portable electronic devices may also be somewhat
smaller devices. Examples of smaller portable electronic devices
include wrist-watch devices, pendant devices, headphone and
earpiece devices, and other wearable and miniature devices. With
one suitable arrangement, which is sometimes described herein as an
example, the portable electronic devices may be handheld electronic
devices.
Examples of portable and handheld electronic devices include
cellular telephones, media players with wireless communications
capabilities, handheld computers (also sometimes called personal
digital assistants), remote controls, global positioning system
(GPS) devices, and handheld gaming devices. The devices may also be
hybrid devices that combine the functionality of multiple
conventional devices. Examples of hybrid devices include a cellular
telephone that includes media player functionality, a gaming device
that includes a wireless communications capability, a cellular
telephone that includes game and email functions, and a handheld
device that receives email, supports mobile telephone calls, has
music player functionality and supports web browsing. These are
merely illustrative examples.
An illustrative portable electronic device such as a handheld
electronic device in accordance with an embodiment of the present
invention is shown in FIG. 1. Device 10 may be any suitable
portable or handheld electronic device.
Device 10 may handle communications over one or more communications
bands. For example, wireless communications circuitry in device 10
may be used to handle cellular telephone communications in one or
more frequency bands and data communications in one or more
communications bands. Typical data communications bands that may be
handled by the wireless communications circuitry in device 10
include the 2.4 GHz band that is sometimes used for Wi-Fi.RTM.
(IEEE 802.11) and Bluetooth.RTM. communications, the 5.4 GHz band
that is sometimes used for Wi-Fi communications, the 1575 MHz
Global Positioning System band, and 3 G data bands (e.g., the UMTS
band at 1920-2170). These bands may be covered by using single and
multiband antennas. For example, cellular telephone communications
can be handled using a multiband cellular telephone antenna and
local area network data communications can be handled using a
multiband wireless local area network antenna. As another example,
a device 10 may have a single multiband antenna for handling
communications in two or more data bands (e.g., at 2.4 GHz and at
5.4 GHz). If desired, the antenna structures in device 10 may be
used to implement multiple-in-multiple out (MIMO) schemes such as
those used in supporting the IEEE 802.11n standard and in
high-capacity cellular telephones, etc.
Device 10 may have housing 12. Housing 12, which is sometimes
referred to as a case, may be formed of any suitable materials
including plastic, glass, ceramics, metal, other suitable
materials, or a combination of these materials. In some situations,
housing 12 or portions of housing 12 may be formed from a
dielectric or other low-conductivity material, so that operation of
conductive antenna elements that are located in proximity to
housing 12 is not disrupted by the housing. Housing 12 or portions
of housing 12 may also be formed from conductive materials such as
metal. An illustrative metal housing material that may be used is
anodized aluminum. Aluminum is relatively light in weight and, when
anodized, has an attractive insulating and scratch-resistant
surface. If desired, other metals can be used for the housing of
device 10, such as stainless steel, magnesium, titanium, alloys of
these metals and other metals, etc. In scenarios in which housing
12 is formed from metal elements, one or more of the metal elements
may be used as part of the antenna in device 10. For example, metal
portions of housing 12 and metal components in housing 12 may be
shorted together to form a ground plane in device 10 or to expand a
ground plane structure that is formed from a planar circuit
structure as a printed circuit board structure (e.g., a printed
circuit board structure used in forming antenna structures for
device 10).
Device 10 may have one or more buttons such as buttons 14. Buttons
14 may be formed on any suitable surface of device 10. In the
example of FIG. 1, buttons 14 have been formed on the top surface
of device 10.
If desired, device 10 may have a display such as display 16.
Display 16 may be a liquid crystal diode (LCD) display, an organic
light emitting diode (OLED) display, a plasma display, or any other
suitable display. The outermost surface of display 16 may be formed
from one or more plastic or glass layers. If desired, touch screen
functionality may be integrated into display 16 or may be provided
using a separate touch pad device. An advantage of integrating a
touch screen into display 16 to make display 16 touch sensitive is
that this type of arrangement can save space and reduce visual
clutter. Buttons 14 may, if desired, be arranged adjacent to
display 16. With this type of arrangement, the buttons may be
aligned with on-screen options that are presented on display 16. A
user may press a desired button to select a corresponding one of
the displayed options.
Device 10 may have circuitry 18. Circuitry 18 may include storage,
processing circuitry, and input-output components. Wireless
transceiver circuitry in circuitry 18 may be used to transmit and
receive radio-frequency (RF) signals. Transmission lines such as
coaxial transmission lines and microstrip transmission lines may be
used to convey radio-frequency signals between transceiver
circuitry and antenna structures in device 10. As shown in FIG. 1,
for example, transmission line 22 may be used to convey signals
between antenna structure 20 and circuitry 18. Transmission line 22
may be, for example, a coaxial cable that is connected between an
RF transceiver (sometimes called a radio) and a multiband
antenna.
A schematic diagram of an embodiment of an illustrative portable
electronic device is shown in FIG. 2. Portable device 10 may be a
mobile telephone, a mobile telephone with media player
capabilities, a handheld computer, a remote control, a game player,
a global positioning system (GPS) device, a combination of such
devices, or any other suitable portable or handheld electronic
device.
As shown in FIG. 2, portable device 10 may include storage 34.
Storage 34 may include one or more different types of storage such
as hard disk drive storage, nonvolatile memory (e.g., flash memory
or other electrically-programmable-read-only memory), volatile
memory (e.g., battery-based static or dynamic
random-access-memory), etc.
Processing circuitry 36 may be used to control the operation of
device 10. Processing circuitry 36 may be based on a processor such
as a microprocessor and other suitable integrated circuits. With
one suitable arrangement, processing circuitry 36 and storage 34
are used to run software on device 10, such as internet browsing
applications, voice-over-internet-protocol (VOIP) telephone call
applications, email applications, media playback applications,
operating system functions, etc. Processing circuitry 36 and
storage 34 may be used in implementing suitable communications
protocols. Communications protocols that may be implemented using
processing circuitry 36 and storage 34 include internet protocols,
wireless local area network protocols (e.g., IEEE 802.11
protocols--sometimes referred to as Wi-Fi.RTM.), protocols for
other short-range wireless communications links such as the
Bluetooth.RTM. protocol, protocols for handling 3 G data services
such as UMTS, cellular telephone communications protocols, etc.
Input-output devices 38 may be used to allow data to be supplied to
device 10 and to allow data to be provided from device 10 to
external devices. Display screen 16 and buttons 14 of FIG. 1 are
examples of input-output devices 38.
Input-output devices 38 may include user input-output devices 40
such as buttons, touch screens, joysticks, click wheels, scrolling
wheels, touch pads, key pads, keyboards, microphones, cameras,
speakers, tone generators, vibrating elements, etc. A user can
control the operation of device 10 by supplying commands through
user input devices 40.
Display and audio devices 42 may include liquid-crystal display
(LCD) screens or other screens, light-emitting diodes (LEDs), and
other components that present visual information and status data.
Display and audio devices 42 may also include audio equipment such
as speakers and other devices for creating sound. Display and audio
devices 42 may contain audio-video interface equipment such as
jacks and other connectors for external headphones and
monitors.
Wireless communications devices 44 may include communications
circuitry such as radio-frequency (RF) transceiver circuitry formed
from one or more integrated circuits, power amplifier circuitry,
passive RF components, one or more antennas (e.g., antenna
structures such as antenna structures 20 of FIG. 1), and other
circuitry for handling RF wireless signals. Wireless signals can
also be sent using light (e.g., using infrared communications).
Device 10 can communicate with external devices such as accessories
46 and computing equipment 48, as shown by paths 50. Paths 50 may
include wired and wireless paths. Accessories 46 may include
headphones (e.g., a wireless cellular headset or audio headphones)
and audio-video equipment (e.g., wireless speakers, a game
controller, or other equipment that receives and plays audio and
video content).
Computing equipment 48 may be any suitable computer. With one
suitable arrangement, computing equipment 48 is a computer that has
an associated wireless access point or an internal or external
wireless card that establishes a wireless connection with device
10. The computer may be a server (e.g., an internet server), a
local area network computer with or without internet access, a
user's own personal computer, a peer device (e.g., another handheld
electronic device 10), or any other suitable computing
equipment.
The antenna structures and wireless communications devices of
device 10 may support communications over any suitable wireless
communications bands. For example, wireless communications devices
44 may be used to cover communications frequency bands such as the
cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900
MHz, data service bands such as the 3 G data communications band at
2100 MHz band (commonly referred to as UMTS or Universal Mobile
Telecommunications System), Wi-Fi.RTM. (IEEE 802.11) bands (also
sometimes referred to as wireless local area network or WLAN
bands), the Bluetooth.RTM. band at 2.4 GHz, and the global
positioning system (GPS) band at 1575 MHz. Wi-Fi bands that may be
supported include the 2.4 GHz band and the 5.0 GHz bands. The 5.0
GHz Wi-Fi bands extend from 5.15-5.85 GHz and are sometimes
referred to by their approximate center frequency of 5.4 GHz (i.e.,
these communications frequencies are sometimes referred to as
making up a 5.4 GHz communications band). Device 10 can cover these
communications bands and/or other suitable communications bands
with proper configuration of the antenna structures in wireless
communications circuitry 44.
A top view of illustrative antenna structures in accordance with an
embodiment of the present invention is shown in FIG. 3. As shown in
FIG. 3, antenna 20 may be formed from a ground plane structure such
as ground plane 52. Ground plane 52 may be formed from a printed
circuit board, a planar metal structure, conductive electrical
components, conductive housing walls, other suitable conductive
structures, or combinations of these structures. With one suitable
arrangement, ground plane 52 may be formed from one or more
conductive layers on a printed circuit board. The printed circuit
board may be rigid or flexible. An example of a rigid circuit board
substrate is fiberglass-filled epoxy (e.g., FR4). An example of a
flexible printed circuit board material is polyimide. Flexible
printed circuits are sometimes referred to as flex circuits and may
be mounted to dielectric support structures such as plastic
supports.
Antenna resonating elements for antenna 20 may be formed from
openings in ground plane 52. In the example of FIG. 3, there are
two openings in ground plane 52: opening 54 and opening 56. These
openings are typically filled with air, but may, if desired, be
filled with other suitable dielectrics such as plastic. Because
openings such as openings 54 and 56 have lengths that are typically
longer than their widths, openings of this type are often referred
to as slots.
Slots 54 and 56 serve as antenna resonating elements for antenna
20, whereas ground plane 52 serves as a ground plane element for
antenna 20. The slots and ground plane are sometimes referred to as
forming "poles" for antenna 20. For example, a first antenna
structure may be formed by slot 54 (which serves as a first of two
antenna poles for the first antenna structure) and ground plane 52
(which serves as a second of two antenna poles for the first
antenna structure). Similarly, a second antenna structure can be
formed from slot 56 (which serves as a first of two antenna poles
for the second antenna structure) and ground plane 52 (which serves
as a second of two antenna poles for the second antenna structure).
Slots 54 and 56 may resonate at different frequencies, so that the
antenna that is formed from slots 54 and 56 (and from ground plane
52) serves as a multiband antenna. The antenna structure formed
from slot 54 and ground plane 52 may handle a first communications
band, whereas the antenna structure formed from slot 56 and ground
plane 52 may handle a second communications band.
Slots 54 and 56 may have any suitable shapes. For example, slot 54
may be completely surrounded by portions of ground plane element 52
(as with slot 56) or may have openings (as with opening 58 of slot
54). In a typical configuration, slots 54 and 56 are relatively
long and thin. With this type of configuration, slots 54 and 56
have longitudinal dimensions that significantly exceed their
lateral dimensions.
Any suitable feed arrangement may be used to feed antenna 20. As
shown schematically in the example of FIG. 3, a transmission line
such as coaxial transmission line may be used to convey
radio-frequency signals between antenna 20 and a radio-frequency
transceiver such as radio-frequency transceiver 60. Transceiver
circuitry 60 may include one or more transceivers for handling
communications in one or more discrete communications bands. For
example, transceiver circuitry 60 may be used to handle
communications in 2.4 GHz and 5.4 GHz communications bands.
Transmission line 22 may be coupled to antenna 20 at feed terminals
such as feed terminals 62 and 64. Feed terminal 64 may be referred
to as a ground or negative feed terminal and may be shorted to the
outer (ground) conductor of transmission line 22. Feed terminal 62
may be referred to as the positive antenna terminal. Transmission
line center conductor 68 may be used to connect transmission line
22 to positive feed terminal 62. If desired, other types of antenna
coupling arrangements may be used (e.g., based on near-field
coupling, using impedance matching networks, etc.).
As shown schematically by dotted line 66 in FIG. 3, the feed
arrangement for antenna 3 may include a matching network. Matching
network 66 may include a balun (to match an unbalanced transmission
line to a balanced antenna or to match a balanced transmission line
to an unbalanced antenna) and/or an impedance transformer (to help
match the impedance of the transmission line to the impedance of
the antenna).
In the example of FIG. 3, slot 54 has a length L1 and a width W1,
whereas slot 56 has a length L2 and a width W2. Slot widths W1 and
W2 may be, for example, about 0.1 to 0.5 mm. The use of relatively
small slot widths W1 and W2 may help reduce the length of the
center conductor 68 (or comparable conductive structures used in
matching network 66). If feed structures such as center conductor
68 are too large, their lengths may approach a quarter of a
wavelength at the radio frequencies being handled by transceiver
60. This could cause center conductor 68 to resonate, thereby
reducing efficiency. Because relatively small slot widths W1 and W2
may allow use of a reduced feed width (i.e., a smaller lateral
spacing between positive antenna feed terminal 62 and ground
terminal 64), the use of small slot widths W1 and W2 may enhance
antenna efficiency.
The length associated with open slot such as slot 54 may be
substantially equal to a quarter of a wavelength at the slot's
frequency of operation. For example, the length L1 of open-ended
slot 54 may be substantially equal to a quarter of a wavelength in
a first communications band (i.e., at 2.4 GHz). The length of a
close-ended slot such as closed slot 56 may be substantially equal
to half of a wavelength at the slot's frequency of operation. For
example, the length L2 of close-ended slot 56 may be substantially
equal to half of a wavelength in a second communications band
(i.e., at 5.4 GHz). With this illustrative configuration, the
lengths L1 and L2 may be, for example, about 10-20 mm (e.g., about
16 mm).
An advantage of arrangements of the type shown in FIG. 3 in which
an open-ended slot such as slot 54 is used to cover a lower
frequency band while a close-ended slot such as slot 56 is used to
cover a higher frequency band is that this prevents the slot that
is associated with the lower frequency band from being much longer
than the slot that is associated with the upper frequency band and
allows the size of antenna 20 to be minimized. For example, the use
of an open-ended geometry for slot 54 in the FIG. 3 arrangement
allows the length of slot 54 to be roughly equal to the length of
slot 56, even though slot 54 is used to cover a frequency band at
roughly half of the frequency of the frequency band associated with
slot 56.
Slot 54 and/or slot 56 may contain portions that are not straight.
In the illustrative arrangement of FIG. 3, for example, slot 56 has
angled portion 70. Angled portion 70 has a longitudinal axis (i.e.,
main longitudinal axis 72 of slot 56) that is oriented at an angle
.alpha. with respect to main longitudinal axis 74 of slot 54. Angle
.alpha. may have a value of 10-45.degree., a value of 5-85.degree.,
or a value of 15-40.degree. (as examples). The use of a non-zero
angle .alpha. between slots 54 and 56 in antenna 20 helps to reduce
near-field electromagnetic coupling between slots 54 and 56. Such
near-field coupling can create antenna losses, so the use of a
non-zero angle to separate slots 54 and 56 can help to improve
antenna efficiency.
As shown in FIG. 3, a slot in antenna 20 such as slot 56 may have a
portion such as portion 76 that is angled (bent). Bent portion 76
may have an associated axis (longitudinal axis 78) that is oriented
at a non-zero angle .beta. with respect to axis 80. Axis 80 is
aligned with a central portion of slot 56 (i.e., a portion of slot
56 that lies between angled portion 70 and angled portion 76) and
is aligned with main longitudinal axis 74 of slot 54. In the
example of FIG. 3, axis 78 and axis 80 are oriented at right angles
with respect to each other (i.e., angle .beta. is 90.degree. in
FIG. 3). If desired, end portion 76 can be angled at other angles
(e.g., angles .beta. of between 70.degree. and 110.degree.). The
use of a 90.degree. angle in the FIG. 3 arrangement is merely
illustrative.
Because end portion 76 is angled, the footprint associated with
slot 56 may be reduced in size. This may help ensure that slots 54
and 56 and ground plane element 52 can be accommodated within the
potentially tight confines of housing 12. Angled end portion 76 may
also help to match the impedance of slot 56 to the impedance of the
antenna feed (e.g., transmission line 22).
Portion 76 of slot 56 may have an associated length L3 along
longitudinal axis 78 and may have a width W3. The length L3 of
portion 76 is typically significantly smaller than overall slot
length L2. With one illustrative arrangement, the width W3 is
greater than width W2. For example, in configurations in which
width W2 is about 0.1 to 0.5 mm, width W3 may be 0.6 mm to several
mm (as an example).
The larger width of angled portion 76 relative to the other
portions of slot 56 may help to increase the bandwidth of slot 56.
This is illustrated in FIG. 4. FIG. 4 is a graph in which the
standing wave ratio (SWR) for an antenna such as antenna 20 of FIG.
3 has been plotted as a function of frequency. As shown in FIG. 4,
antenna 20 of FIG. 3 covers a lower frequency band at 2.4 GHz and a
higher frequency band at 5.4 GHz. Because of the presence of
widened end portion 76 in slot 56, the antenna bandwidth in the 5.4
GHz band (which is associated with slot 56) is larger than the
antenna bandwidth in the 2.4 GHz band (which is associated with
slot 54). This type of behavior may be helpful when the higher
frequency band (e.g., the 5.4 GHz band in the FIG. 4 example)
requires a relatively larger bandwidth than the lower frequency
band.
Slots 54 and 56 may be configured so that the second harmonic of
the lower-frequency slot (slot 54) coincides with the
higher-frequency band (directly or at a slight frequency offset).
In this type of situation, the frequency response of the
fundamental harmonic of slot 56 (e.g., at 5.4 GHz) may be widened
due to both the presence of end portion 76 and the frequency
response contribution of the second harmonic of lower-frequency
slot 54. If desired, the low frequency slot in antenna 20 (e.g.,
antenna slot 54) may be provided with a widened end portion in
addition to or as an alternative to providing slot 56 with widened
end portion 76.
As shown in FIG. 3, widened end portion 76 may have a substantially
rectangular shape. If desired, other shapes may be used for end
portion 76 (e.g., portions with curved sides or other
non-rectangular shapes). The use of a rectangular widened end
portion 76 in the arrangement of FIG. 3 is merely illustrative.
FIG. 5 shows an alternative layout that may be used for slot 54. As
shown in the arrangement of FIG. 5, slot 54 in antenna 20 may have
an opening 58 that is not completely aligned with edge 82 of ground
plane 52. Nevertheless, arrangements of the type shown in FIG. 5
may provide satisfactory antenna performance. In certain device
configurations, omitting a corner of ground plane 52 as shown in
FIG. 5 may help ground plane 52 fit within housing 12 of device
10.
Another possibly slot geometry is shown in FIG. 6. In the FIG. 6
example, slot 54 has angled end portion 84. Angled end portion 84
may be angled at any suitable angle with respect to longitudinal
axis 74. For example, angled end portion 84 may be oriented so that
its longitudinal axis lies perpendicular to axis 74 as shown in
FIG. 6. The width of slot portion 84 may be the same as the width
of the other portions of slot 54 or may be different (e.g., wider
or narrower). As with arrangements of the type shown in FIG. 5, the
use of bent slot portion 84 in slot 54 may help antenna 20
accommodate design constraints such as constraints imposed by the
geometry of device housing 12.
FIG. 7 shows how slot 56 may have an angled portion such as angled
portion 86. Angled portion 86 and widened end portion 76 may be
formed at opposite ends of slot 56. Angled end portion 86 may be
oriented at any suitable angle with respect to the other portions
of slot 56. For example, angled end portion 86 may be oriented so
that its longitudinal axis is perpendicular to main longitudinal
axis 72 of slot 56 as shown in FIG. 7. Portion 86 may have the same
width as the central portion of slot 56 or may be wider or narrower
than the central portion of slot 56. The use of an angled portion
such as angled portion 86 may help antenna 20 accommodate layout
constraints (as an example).
Slot features such as uneven slot end 58 of slot 54 in FIG. 5,
angled portion 84 of open slot 54 of FIG. 6, angled and widened
slot portion 76 of slot 56 of FIG. 3, angled slot portion 70 of
slot 56 of FIG. 3, and angled end portion 86 of closed slot 56 of
FIG. 7 may be used in any desired combination. The geometries of
slots 54 and 56 that are shown in FIGS. 3, 5, 6, and 7 are merely
illustrative.
If desired, antenna 20 may be integrated into a wall of housing 12
or may be otherwise mounted to an exterior portion of device 10.
This type of arrangement is shown in the cross-sectional view of
FIG. 8. As shown in FIG. 8, housing 12 may have housing wall
portions 12A, 12B, and 12C that define slots such as slots 56 and
54. Slots 54 and 56 may be filled with air or other suitable
dielectric. Dielectric antenna feed structure 88 may be mounted to
the interior of housing 12 in device 10. Structure 88 may be formed
from a layer of flex circuit or other suitable dielectric
materials. Vias such as vias 90 and 92 may be used to provide
conductive pathways through dielectric structure 88. Vias 90 and 92
may be formed from metal or other suitable conductors. An example
of a metal that may be used to form vias 90 and 92 is nickel.
Conductive pads such as pads 94 and 96 may be formed on the
interior surface of dielectric support structure 88. Pads 94 and 96
may be formed of metal or any other suitable conductive material.
Similar pads may be formed on the opposing surface of dielectric
support 88 to facilitate electrical contact between vias 90 and 92
and conductive housing wall portions 12A and 12C.
Pads 94 and 96 may serve as ground and positive antenna feed
terminals for antenna 20. In the schematic representation of FIG.
8, antenna terminals 62 and 64 are shown as being fed using a
coaxial cable 22. The coaxial cable may have an outer ground
conductor that is electrically connected to ground antenna terminal
64 and may have a center conductor such as center conductor 68 that
is electrically connected to positive antenna terminal 62. This is,
however, merely illustrative. Any suitable transmission line and/or
matching network structures may be used to feed antenna terminals
62 and 64. The arrangement of FIG. 8 is presented as an
example.
The foregoing is merely illustrative of the principles of this
invention and various modifications can be made by those skilled in
the art without departing from the scope and spirit of the
invention.
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